High quality image copier with exact reproduction of digitally halftoned images

ABSTRACT

The invention relates to a method of generating print data from a printed image produced by a printing device operating at a first dots per inch (dpi) value, so that the image is composed of a plurality of dots, the image incorporating defects resulting during printing of the image, such as rotation of a print medium and blemishes of the image. The method includes the step of scanning the printed image, at a sampling rate which corresponds to a second dpi value that exceeds the first dpi value by a predetermined factor so that each dot of the image results in the generation of at least two markers. Data relating to the position and colour value of each marker is generated. The defects in the image are detected and a data value is assigned to such defects. The data is processed and the data value is used to determine which of each of the markers generated for a respective dot should be recorded as a center for that dot. Print data is generated as a result of the processing step, the print data relating to the position and print value of the markers determined as a result of processing the data.

CROSS REFERENCES TO RELATED APPLICATIONS

The following Austrailian provisional patent applications are hereby incorporated by cross-reference. For the purposes of location and identification, U.S. patent applications identified by their U.S. patent application serial numbers (USSN) are listed alongside the Austrailian applications from which the U.S. patent applications claim the right of priority.

CROSS-REFERENCED U.S. PATENT/ AUSTRALIAN PATENT APPLICATION PROVISIONAL (CLAIMING RIGHT OF PATENT PRIORITY FROM AUSTRALIAN DOCKET APPLICATION NO. PROVISIONAL APPLICATION) NO. PO7991 09/113,060 ART01 PO8505 09/113,070 ART02 PO7988 09/113,073 ART03 PO9395 09/112,748 ART04 PO8017 09/112,747 ART06 PO8014 09/112,776 ART07 PO8025 09/112,750 ART08 PO8032 09/112,746 ART09 PO7999 09/112,743 ART10 PO7998 09/112,742 ART11 PO8031 09/112,741 ART12 PO8030 09/112,740 ART13 PO7997 09/112,739 ART15 PO7979 09/113,053 ART16 PO8015 09/112,738 ART17 PO7978 09/113,067 ART18 PO7982 09/113,063 ART19 PO7989 09/113,069 ART20 PO8019 09/112,744 ART21 PO7980 09/113,058 ART22 PO8018 09/112,777 ART24 PO7938 09/113,224 ART25 PO8016 09/112,804 ART26 PO8024 09/112,805 ART27 PO7940 09/113,072 ART28 PO7939 09/112,785 ART29 PO8501 09/112,797 ART30 PO8500 09/112,796 ART31 PO7987 09/113,071 ART32 PO8022 09/112,824 ART33 PO8497 09/113,090 ART34 PO8020 09/112,823 ART38 PO8023 09/113,222 ART39 PO8504 09/112,786 ART42 PO8000 09/113,051 ART43 PO7977 09/112,782 ART44 PO7934 09/113,056 ART45 PO7990 09/113,059 ART46 PO8499 09/113,091 ART47 PO8502 09/112,753 ART48 PO7981 09/113,055 ART50 PO7986 09/113,057 ART51 PO7983 09/113,054 ART52 PO8026 09/112,752 ART53 PO8027 09/112,759 ART54 PO8028 09/112,757 ART56 PO9394 09/112,758 ART57 PO9396 09/113,107 ART58 PO9397 09/112,829 ART59 PO9398 09/112,792 ART60 PO9399 6,106,147 ART61 PO9400 09/112,790 ART62 PO9401 09/112,789 ART63 PO9402 09/112,788 ART64 PO9403 09/112,795 ART65 PO9405 09/112,749 ART66 PP0959 09/112,784 ART68 PP1397 09/112,783 ART69 PP2370 09/112,781 DOT01 PP2371 09/113,052 DOT02 PO8003 09/112,834 Fluid01 PO8005 09/113,103 Fluid02 PO9404 09/113,101 Fluid03 PO8066 09/112,751 IJ01 PO8072 09/112,787 IJ02 PO8040 09/112,802 IJ03 PO8071 09/112,803 IJ04 PO8047 09/113,097 IJ05 PO8035 09/113,099 IJ06 PO8044 09/113,084 IJ07 PO8063 09/113,066 IJ08 PO8057 09/112,778 IJ09 PO8056 09/112,779 IJ10 PO8069 09/113,077 IJ11 PO8049 09/113,061 IJ12 PO8036 09/112,818 IJ13 PO8048 09/112,816 IJ14 PO8070 09/112,772 IJ15 PO8067 09/112,819 IJ16 PO8001 09/112,815 IJ17 PO8038 09/113,096 IJ18 PO8033 09/113,068 IJ19 PO8002 09/113,095 IJ20 PO8068 09/112,808 IJ21 PO8062 09/112,809 IJ22 PO8034 09/112,780 IJ23 PO8039 09/113,083 IJ24 PO8041 09/113,121 IJ25 PO8004 09/113,122 IJ26 PO8037 09/112,793 IJ27 PO8043 09/112,794 IJ28 PO8042 09/113,128 IJ29 PO8064 09/113,127 IJ30 PO9389 09/112,756 IJ31 PO9391 09/112,755 IJ32 PP0888 09/112,754 IJ33 PP0891 09/112,811 IJ34 PP0890 09/112,812 IJ35 PP0873 09/112,813 IJ36 PP0993 09/112,814 IJ37 PP0890 09/112,764 IJ38 PP1398 09/112,765 IJ39 PP2592 09/112,767 IJ40 PP2593 09/112,768 IJ41 PP3991 09/112,807 IJ42 PP3987 09/112,806 IJ43 PP3985 09/112,820 IJ44 PP3983 09/112,821 IJ45 PO7935 09/112,822 IJM01 PO7936 09/112,825 IJM02 PO7937 09/112,826 IJM03 PO8061 09,112,827 IJM04 PO8054 09/112,828 IJM05 PO8065 6,071,750 IJM06 PO8055 09/113,108 IJM07 PO8053 09/113,109 IJM08 PO8078 09/113,123 IJM09 PO7933 09/113,114 IJM10 PO7950 09/113,115 IJM11 PO7949 09/113,129 IJM12 PO8060 09/113,124 IJM13 PO8059 09/113,125 IJM14 PO8073 09/113,126 IJM15 PO8076 09/113,119 IJM16 PO8075 09/113,120 IJM17 PO8079 09/113,221 IJM18 PO8050 09/113,116 IJM19 PO8052 09/113,118 IJM20 PO7948 09/113,117 IJM21 PO7951 09/113,113 IJM22 PO8074 09/113,130 IJM23 PO7941 09/113,110 IJM24 PO8077 09/113,112 IJM25 PO8058 09/113,087 IJM26 PO8051 09/113,074 IJM27 PO8045 6,110,754 IJM28 PO7952 09/113,088 IJM29 PO8046 09/112,771 IJM30 PO9390 09/112,769 IJM31 PO9392 09/112,770 IJM32 PP0889 09/112,798 IJM35 PP0887 09/112,801 IJM36 PP0882 09/112,800 IJM37 PP0874 09/112,799 IJM38 PP1396 09/113,098 IJM39 PP3989 09/112,833 IJM40 PP2591 09/112,832 IJM41 PP3990 09/112,831 IJM42 PP3986 09/112,830 IJM43 PP3984 09/112,836 IJM44 PP3982 09/112,835 IJM45 PP0895 09/113,102 IR01 PP0870 09/113,106 IR02 PP0869 09/113,105 IR04 PP0887 09/113,104 IR05 PP0885 09/112,810 IR06 PP0884 09/112,766 IR10 PP0886 09/113,085 IR12 PP0871 09/113,086 IR13 PP0876 09/113,094 IR14 PP0877 09/112,760 IR16 PP0878 09/112,773 IR17 PP0879 09/112,774 IR18 PP0883 09/112,775 IR19 PP0880 6,152,619 IR20 PP0881 09/113,092 IR21 PO8006 6,087,638 MEMS02 PO8007 09/113,093 MEMS03 PO8008 09/113,062 MEMS04 PO8010 6,041,600 MEMS05 PO8011 09/113,082 MEMS06 PO7947 6,067,797 MEMS07 PO7944 09/113,080 MEMS09 PO7946 6,044,646 MEMS10 PO9393 09/113,065 MEMS11 PP0875 09/113,078 MEMS12 PP0894 09/113,075 MEMS13

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not applicable.

FIELD OF THE INVENTION

The present invention relates to an image processing method and apparatus and, in particular, discloses a high quality copier.

The present invention further relates to the reproduction of images.

BACKGROUND OF THE INVENTION

Recently, a camera printing system has been proposed by the present applicant which involves the printing out of images via an inkjet printing device, the images being imaged by a camera CCD array or the like and printed out via an integral printer.

One extremely popular form of camera technology is the traditional negative film and positive print photographs. In this case, a camera is utilized to image a scene onto a negative which is then processed so as to fix the negative. Subsequently, a set of prints is made from the negative. Further sets of prints can be instantly created at any time from the set of negatives. The prints normally have a resolution close to that of the original set of prints.

Unfortunately, with digital camera devices, including those proposed by the present applicant, it would be necessary to permanently store in a digital form the photograph captured and printed out if further copies of the image were desired at a later time. This would be generally inconvenient in that, ideally, a copy of a “photograph” should merely require the initial print.

Of course, alternatively, the original print may be copied utilising a high quality colour photocopying device. Unfortunately, any such device has limited copy capabilities and signal degradation will often be the result when such a form of copying is used.

Obviously, more suitable forms of producing copies of camera prints are desirable.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a high quality method of reproduction of scanned images.

According to a first aspect of the invention, there is provided a method of generating print data from a printed image produced by a printing device operating at a first dots per inch (dpi) value so that the image is composed of a plurality of dots, the image incorporating defects resulting during printing of the image, such as rotation of a print medium and blemishes of the image, the method comprising the steps of:

scanning the printed image, at a sampling rate which corresponds to a second dpi value that exceeds the first dpi value by a predetermined factor, which is such that each dot of the image results in the generation of a set of at least two markers;

generating data relating to the position and colour value of each marker;

detecting the defects in the image and assigning a data value to such defects;

processing said data and applying the data value assigned to the defects to determine which of each of the markers generated for a respective dot should be recorded as a centre for that dot; and

generating print data as a result of the processing step, the print data relating to the position and print value of the markers determined as a result of processing the data.

According to a second aspect of the invention, there is provided an apparatus for generating print data from a printed image, the apparatus comprising

a printing device that operates at a first dots per inch (dpi) value to generate the printed image, so that the image is composed of a plurality of dots, the image incorporating defects resulting during printing of the image, such as rotation of a print medium and blemishes of the image;

a scanning device positioned downstream of the printing device for scanning the printed image, the scanning device being configured to operate at a sampling rate which corresponds to a second dpi value that exceed the first dpi value by a predetermined factor, which is such that each dot of the image results in the generation of a set of at least two markers, the scanning device being configured to generate data relating to the position and colour value of each marker; and

a processor that is connected to the scanning device and is configured to receive said data from the scanning device, the processor being capable of analysing said data for the defects, applying a data value to the defects, and processing said data together with the data value to determine which of each of the markers generated for a respective dot should be recorded as a centre for that dot, and generating print data relating to the position and colour value of the markers so determined.

BRIEF DESCRIPTION OF THE DRAWINGS

Notwithstanding any other forms which may fall within the scope of the present invention, preferred forms of the invention will now be described, by way of example only, with reference to the accompanying drawings in which:

FIG. 1 illustrates the structure of a high resolution printed image;

FIG. 1A is an enlarged view of the high resolution printed image of FIG. 1.

FIG. 2 illustrates an apparatus for processing the image of FIG. 1 so as to produce a copy;

FIG. 3 illustrates centroid processing steps;

FIG. 4 illustrates a series pulsable patterns generated as a result of the processing steps.

DESCRIPTION OF PREFERRED AND OTHER EMBODIMENTS

The preferred embodiment is preferably implemented through a suitably programmed of a hand held camera device such as that described in co-pending U.S. patent application Ser. No. 09/113,060 entitled “Digital Instant Printing Camera with Image Processing Capability” (Docket ART 01); filed concurrently herewith by the present applicant the content of which is hereby specifically incorporated by cross reference.

The aforementioned patent specification discloses a camera system, hereinafter known as an “Artcam” type camera, wherein sensed images can be directly printed out by an Artcam portable camera unit. Further, the aforementioned specification discloses means and methods for performing various manipulations on images captured by the camera sensing device leading to the production of various effects in any output image. The manipulations disclosed are highly flexible in nature and can be implemented through the insertion into the Artcam of cards having encoded thereon various instructions for the manipulation of images, the cards hereinafter being known as Artcards. The Artcam further has significant onboard processing power as a result of an Artcam Central Processor unit (ACP) which is interconnected to a memory device for the storage of important data and images.

In the preferred embodiment, it is assumed that it is desired to reproduce a camera image taken with a digital image camera and printed out on a print device such as an inkjet printer which has a predetermined dpi (say 1600 dpi) such as that disclosed in the aforementioned patent application.

Turning now to FIG. 1, such a digital imaging camera device 1 is designed to print an image 2 having a standard output resolution. The image 2 is printed out by an inkjet printer device having multi colour outputs (cyan, magenta and yellow) and generating an array of dots 4 (See FIG. 1A) for each colour component of the input image.

When it is desired to create a copy of the outputted photograph 2, the image is first scanned and the relevant colour components are derived.

The method of the preferred embodiment is illustrated in FIG. 2. In this method, the photographic image 2 is scanned utilizing a linear CCD 10 which provides for full colour scanning of images into corresponding colour components. Suitable linear CCD scanners are known in the art. For a description of the construction and operation of linear CCD devices, reference is made to a standard text such as in “CCD arrays, cameras and displays” by Gerald C Holst, published 1996 by SPIE Optical Engineering Press. Further, suitable sensor devices are regularly described in the IEEE Transactions on Consumer Electronics.

It is assumed that the CCD array 10 scans an image passing under the CCD head to produce analogue signals which are converted into digital signals so as to form corresponding 4 bit digital values. The CCD array 10 operates at 4800 dots per inch being three times the dot resolution of a photograph. The CCD 10 can comprise three monocolour filters and CCDs, one for each colour. The rate of 4800 dpi can be achieved by using a series of staggered CCD arrays, each one offset from an adjacent array.

The data values are forwarded to a frame buffer controller 12 and stored in a frame buffer 13 by according to colour components. The stored image is processed to extract the position of the original dots as printed on the photograph and scanned by the CCD at the previously mentioned CCD scanning resolution of approximately three times that with which it was printed. Unfortunately, a number of defects may exist in the scanned image. These include defects associated with this scanning process including the effects of scratches and warping of the photograph 2 in addition to a possible slight rotation of the photograph 2 when fed through the CCD scanner 10.

The procedure for determining the patterns and dots firstly relies on utilizing a process to extract the likely rotation of the photo 2. In order to determine such a likely rotation, many methods can be utilized.

For example, the scanned pattern of ink dots will have certain fundamental characteristic frequencies which will be dependent upon the rotation. As the ink is printed on the photo utilizing a regular array of dots, the Fourier transform of the image can be analyzed to determine a likely rotation. Alternatively, the edges of the card can be determined from the abrupt boundary of the photo and the underneath scanning surface of the CCD. Further, an expected dot pitch of the pixels (1600 dpi) can be determined.

Starting from one border of the photograph, the scanned image of the photograph is then processed so as to determine whether a dot is located at each possible output dot location. Importantly, a method is utilized to maintain local synchronisation across the card as it is processed to determine likely output dots. It will be evident that local variations in spacings from one column to the next will be extremely minor, with the main variations occurring gradually over the length of the image.

Having determined the rotation and the likely spacing between adjacent dots, one form of processing is to keep a column of likely dot centres (herein after known as “centroids”) and to update the centroids in a column by column manner. Turning to FIG. 3, there is illustrated one form of centroid processing wherein an area of an image 20 is shown having example ink dots 21 on the surface portion of a card. The size of each ink dot 21 for each pixel is approximately three times the corresponding pixel sample rate. A series of centroid markers 22 to 25 are kept for each column. For the centroid markers 23, 24 of column C_(n)+1, the centroid markers of a previously calculated column and the centroid markers 22, 25 for the adjacent column C_(n) are utilized to determine an initial likely centroid location. For example, in order to determine an initial position of centroid marker 23 the centroid markers 22, 24 and 25 are utilized to determine a likely location of centroid marker 23. Once an initial likely location has been determined, the pixel values around the centroid marker 23 are examined so as to determine whether any minute adjustment of the centroid marker 23 is required.

The decision to move a centroid 23 from its expected location is derived by examining pixel values around the point 23. The examination can occur independently in the X and Y direction and the movement can also occur independently in these directions.

Many different methods could be utilized. One method for determining whether minute adjustment of the centroid 23 is required will now be discussed with reference to FIG. 4. In this method, it is noted that only a limited number of adjacent ink dot arrangements are possible. These possible arrangements are illustrated as 30 in FIG. 4 which illustrates a current pixel 31 and its two adjacent pixel 32 and 33. Each of the ink dots 31-33 will have approximately three corresponding pixel values as sensed by the CCD scanner. For each pixel pattern 30 in FIG. 4, there is also shown example CCD output values 35 that are likely CCD output values after having been digitally converted. Due to CCD sampling effects and other mechanical and photopic effects, the CCD values 35 of corresponding dot patterns often comprise the equivalent of analogue to digitally converted Gaussian curves or portions of Gaussian curves. Hence, no abrupt edges are normally provided. However, the cross section expected can be examined against those obtained to determine the closest cross section and, provided errors are not too large, the centroid can be adjusted within limits to produce a better fit. In this way, a new centroid position can be obtained in a first dimension. Of course, the centroid adjustment problem is symmetrical in both dimensional directions and the same processing steps can be applied in the other dimension. Numerous other techniques may be utilized including more advanced techniques such as neural network training from sampled images.

Upon determining an adjusted position, the centroid 23 (FIG. 3) is adjusted slightly and the process of centroid determination continues. From the new centroid location, the surrounding sample values are examined to determine whether an on or off ink dot value should be recorded for the particular centroid location.

Returning to FIG. 2, the recorded ink dot values are stored in an ink dot array 16 and subsequently utilized for printing out at the same (1600 dpi) or a different resolution on a printer eg 17 so as to produce a copy of the photograph 18 which is ink dot for ink dot equivalent to the original photo 11.

In this way, a high quality photographic copy is provided for making copies from the original photographs without having to utilize negatives or to digitally store the image separately.

Of course, many refinements may be possible, including utilization of customised real time pipelined architectures for speeding up processing and eliminating the need to store large data sets in the frame buffers or the like.

It would be appreciated by a person skilled in the art that numerous variations and/or modifications may be made to that present invention as shown in the specific embodiment without departing from the spirit or scope of the invention as broadly described. The present embodiment is, therefore, to be considered in all respects to be illustrative and not respective.

Ink Jet Technologies

The embodiments of the invention use an ink jet printer type device. Of course many different devices could be used. However presently popular ink jet printing technologies are unlikely to be suitable.

The most significant problem with thermal inkjet is power consumption. This is approximately 100 times that required for high speed, and stems from the energy-inefficient means of drop ejection. This involves the rapid boiling of water to produce a vapor bubble which expels the ink. Water has a very high heat capacity, and must be superheated in thermal inkjet applications. This leads to an efficiency of around 0.02%, from electricity input to drop momentum (and increased surface area) out.

The most significant problem with piezoelectric inkjet is size and cost. Piezoelectric crystals have a very small deflection at reasonable drive voltages, and therefore require a large area for each nozzle. Also, each piezoelectric actuator must be connected to its drive circuit on a separate substrate. This is not a significant problem at the current limit of around 300 nozzles per printhead, but is a major impediment to the fabrication of pagewidth printheads with 19,200 nozzles.

Ideally, the inkjet technologies used meet the stringent requirements of in-camera digital color printing and other high quality, high speed, low cost printing applications. To meet the requirements of digital photography, new inkjet technologies have been created. The target features include:

low power (less than 10 Watts)

high resolution capability (1,600 dpi or more)

photographic quality output

low manufacturing cost

small size (pagewidth times minimum cross section)

high speed (<2 seconds per page).

All of these features can be met or exceeded by the inkjet systems described below with differing levels of difficulty. Forty-five different inkjet technologies have been developed by the Assignee to give a wide range of choices for high volume manufacture. These technologies form part of separate applications assigned to the present Assignee as set out in the list under the heading CROSS REFERENCES TO RELATED APPLICATIONS.

The inkjet designs shown here are suitable for a wide range of digital printing systems, from battery powered one-time use digital cameras, through to desktop and network printers, and through to commercial printing systems

For ease of manufacture using standard process equipment, the printhead is designed to be a monolithic 0.5 micron CMOS chip with MEMS post processing. For color photographic applications, the printhead is 100 mm long, with a width which depends upon the inkjet type. The smallest printhead designed is IJ38, which is 0.35 mm wide, giving a chip area of 35 square mm. The printheads each contain 19,200 nozzles plus data and control circuitry.

Ink is supplied to the back of the printhead by injection molded plastic ink channels. The molding requires 50 micron features, which can be created using a lithographically micromachined insert in a standard injection molding tool. Ink flows through holes etched through the wafer to the nozzle chambers fabricated on the front surface of the wafer. The printhead is connected to the camera circuitry by tape automated bonding.

Tables of Drop-on-Demand Inkjets

Eleven important characteristics of the fundamental operation of individual inkjet nozzles have been identified. These characteristics are largely orthogonal, and so can be elucidated as an eleven dimensional matrix. Most of the eleven axes of this matrix include entries developed by the present assignee.

The following tables form the axes of an eleven dimensional table of inkjet types.

Actuator mechanism (18 types)

Basic operation mode (7 types)

Auxiliary mechanism (8 types)

Actuator amplification or modification method (17 types)

Actuator motion (19 types)

Nozzle refill method (4 types)

Method of restricting back-flow through inlet (10 types)

Nozzle clearing method (9 types)

Nozzle plate construction (9 types)

Drop ejection direction (5 types)

Ink type (7 types)

The complete eleven dimensional table represented by these axes contains 36.9 billion possible configurations of inkjet nozzle. While not all of the possible combinations result in a viable inkjet technology, many million configurations are viable. It is clearly impractical to elucidate all of the possible configurations. Instead, certain inkjet types have been investigated in detail. Forty-five such inkjet types were filed simultaneously to the present application.

Other inkjet configurations can readily be derived from these forty-five examples by substituting alternative configurations along one or more of the 11 axes. Most of the forty-five examples can be made into inkjet printheads with characteristics superior to any currently available inkjet technology.

Where there are prior art examples known to the inventor, one or more of these examples are listed in the examples column of the tables below. The simultaneously filed patent applications by the present applicant are listed by USSN numbers. In some cases, a printer technology may be listed more than once in a table, where it shares characteristics with more than one entry.

Suitable applications include: Home printers, Office network printers, Short run digital printers, Commercial print systems, Fabric printers, Pocket printers, Internet WWW printers, Video printers, Medical imaging, Wide format printers, Notebook PC printers, Fax machines, Industrial printing systems, Photocopiers, Photographic minilabs etc.

The information associated with the aforementioned 11 dimensional matrix are set out in the following tables.

ACTUATOR MECHANISM (APPLIED ONLY TO SELECTED INK DROPS) Description Advantages Disadvantages Examples Thermal An electrothermal Large force High power Canon Bubblejet 1979 bubble heater heats the ink generated Ink carrier limited Endo et al GB patent to above boiling Simple to water 2,007,162 point, transferring construction Low efficiency Xerox heater-in-pit significant heat to No moving High temperatures 1990 Hawkins et al the aqueous ink. A parts required U.S. Pat. No. 4,899,181 bubble nucleates Fast operation High mechanical Hewlett-Packard TIJ and quickly forms, Small chip area stress 1982 Vaught et al expelling the ink. required for Unusual materials U.S. Pat. No. 4,490,728 The efficiency of actuator required the process is low, Large drive with typically less transistors than 0.05% of the Cavitation causes electrical energy actuator failure being transformed Kogation reduces into kinetic energy bubble formation of the drop. Large print heads are difficult to fabricate Piezo- A piezoelectric Low power Very large area Kyser et al U.S. Pat. No. electric crystal such as lead consumption required for 3,946,398 lanthanum zirconate Many ink types actuator Zoltan (PZT) is electrically can be used Difficult to U.S. Pat. No. 3,683,212 activated, and either Fast operation integrate with 1973 Stemme expands, shears, or High efficiency electronics U.S. Pat. No. 3,747,120 bends to apply High voltage drive Epson Stylus pressure to the ink, transistors Tektronix ejecting drops. required U.S. Ser. No. 09/112,803 Full pagewidth print heads impractical due to actuator size Requires electrical poling in high field strengths during manufacture Electro- An electric field is Low power Low maximum Seiko Epson, Usui et all strictive used to activate consumption strain (approx. JP 253401/96 electrostriction in Many ink types 0.01%) U.S. Ser. No. 09/112,803 relaxor materials can be used Large area such as lead Low thermal required for lanthanum zirconate expansion actuator due to titanate (PLZT) or Electric field low strain lead magnesium strength Response speed is niobate (PMN). required marginal (˜10 μs) (approx. 3.5 High voltage drive V/μm) can be transistors generated required without Full pagewidth difficulty print heads Does not impractical due to require actuator size electrical poling Ferro- An electric field is Low power Difficult to U.S. Ser. No. 09/112,803 electric used to induce a consumption integrate with phase transition Many ink types electronics between the can be used Unusual materials antiferroelectric Fast operation such as PLZSnT (AFE) and (<1 μs) are required ferroelectric (FE) Relatively high Actuators require phase. Perovskite longitudinal a large area materials such as tin strain modified lead High efficiency lanthanum zirconate Electric field titanate (PLZSnT) strength of exhibit large strains around 3 V/μm of up to 1% can be readily associated with the provided AFE to FE phase transition. Electro- Conductive plates Low power Difficult to U.S. Ser. No. 09/112,787; static are separated by a consumption operate 09/112,803 plates compressible or Many ink types electrostatic fluid dielectric can be used devices in an (usually air). Upon Fast operation aqueous application of a environment voltage, the plates The electrostatic attract each other actuator will and displace ink, normally need to causing drop be separated from ejection. The the ink conductive plates Very large area may be in a comb or required to honeycomb achieve high structure, or stacked forces to increase the High voltage drive surface area and transistors may be therefore the force. required Full pagewidth print heads are not competitive due to actuator size Electro- A strong electric Low current High voltage 1989 Saito et al, static pull field is applied to consumption required U.S. Pat. No. 4,799,068 on ink the ink, whereupon Low May be damaged 1989 Miura et al, electrostatic temperature by sparks due to U.S. Pat. No. 4,810,954 attraction air breakdown Tone-jet accelerates the ink Required field towards the print strength increases medium. as the drop size decreases High voltage drive transistors required Electrostatic field attracts dust Permanent An electromagnet Low power Complex U.S. Ser. No. 09/113,084; magnet directly attracts a consumption fabrication 09/112,779 electro- permanent magnet, Many ink types Permanent magnetic displacing ink and can be used magnetic material causing drop Fast operation such as ejection. Rare earth High efficiency Neodymium Iron magnets with a field Easy extension Boron (NdFeB) strength around 1 from single required. Tesla can be used. nozzles to High local Examples are: pagewidth print currents required Samarium Cobalt heads Copper (SaCo) and metalization magnetic materials should be used for in the neodymium long iron boron family electromigration (NdFeB, lifetime and low NdDyFeBNb, resistivity NdDyFeB, etc) Pigmented inks are usually infeasible Operating temperature limited to the Curie temperature (around 540 K.) Soft A solenoid induced Low power Complex U.S. Ser. No. 09/112,751; magnetic a magnetic field in a consumption fabrication 09/113,097; 09/113,066; core soft magnetic core Many ink types Materials not 09/112,779; 09/113,061; electro- or yoke fabricated can be used usually present in 09/112,816; 09/112,772; magnetic from a ferrous Fast operation a CMOS fab such 09/112,815 material such as High efficiency as NiFe, CoNiFe, electroplated iron Easy extension or CoFe are alloys such as from single required CoNiFe [1], CoFe, nozzles to High local or NiFe alloys. pagewidth print currents required Typically, the soft heads Copper magnetic material is metalization in two parts, which should be used for are normally held long apart by a spring. electromigration When the solenoid lifetime and low is actuated, the two resistivity parts attract, Electroplating is displacing the ink. required High saturation flux density is required (2.0-2.1 T is achievable with CoNiFe [1]) Lorenz The Lorenz force Low power Force acts as a U.S. Ser. No. 09/113,099; force acting on a current consumption twisting motion 09/113,077; 09/112,818; carrying wire in a Many ink types Typically, only a 09/112,819 magnetic field is can be used quarter of the utilized. Fast operation solenoid length This allows the High efficiency provides force in a magnetic field to be Easy extension useful direction supplied externally from single High local to the print head, nozzles to currents required for example with pagewidth print Copper rare earth heads metalization permanent magnets. should be used for Only the current long carrying wire need electromigration be fabricated on the lifetime and low print-head, resistivity simplifying Pigmented inks materials are usually requirements. infeasible Magneto- The actuator uses Many ink types Force acts as a Fischenbeck, U.S. Pat. No. striction the giant can be used twisting motion 4,032,929 magnetostrictive Fast operation Unusual materials U.S. Ser. No. 09/113,121 effect of materials Easy extension such as Teffenol- such as Terfenol-D from single D are required (an alloy of terbium, nozzles to High local dysprosium and iron pagewidth print currents required developed at the heads Copper Naval Ordnance High force is metalization Laboratory, hence available should be used for Ter-Fe-NOL). For long best efficiency, the electromigration actuator should be lifetime and low pre-stressed to resistivity approx. 8 MPa. Pre-stressing may be required Surface Ink under positive Low power Requires Silverbrook, EP 0771 tension pressure is held in consumption supplementary 658 A2 and related reduction a nozzle by surface Simple force to effect patent applications tension. The surface construction drop separation tension of the ink is No unusual Requires special reduced below the materials ink surfactants bubble threshold, required in Speed may be causing the ink to fabrication limited by egress from the High efficiency surfactant nozzle. Easy extension properties from single nozzles to pagewidth print heads Viscosity The ink viscosity is Simple Requires Silverbrook, EP 0771 reduction locally reduced to construction supplementary 658 A2 and related select which drops No unusual force to effect patent applications are to be ejected. A materials drop separation viscosity reduction required in Requires special can be achieved fabrication ink viscosity electrothermally Easy extension properties with most inks, but from single High speed is special inks can be nozzles to difficult to achieve engineered for a pagewidth print Requires 100:1 viscosity heads oscillating ink reduction. pressure A high temperature difference (typically 80 degrees) is required Acoustic An acoustic wave is Can operate Complex drive 1993 Hadimioglu et al, generated and without a nozzle circuitry EUP 550,192 focussed upon the plate Complex 1993 Elrod et al, EUP drop ejection region. fabrication 572,220 Low efficiency Poor control of drop position Poor control of drop volume Thermo- An actuator which Low power Efficient aqueous U.S. Ser. No. 09/112,802; elastic relies upon consumption operation requires 09/112,778; 09/112,815; bend differential thermal Many ink types a thermal insulator 09/113,096; 09/113,068; actuator expansion upon can be used on the hot side 09/113,095; 09/112,808; Joule heating is Simple planar Corrosion 09/112,809; 09/112,780; used. fabrication prevention can be 09/113,083; 09/112,793; Small chip area difficult 09/112,794; 09/113,128; required for Pigmented inks 09/113,127; 09/112,756; each actuator may be infeasible, 09/112,755; 09/112,754; Fast operation as pigment 09/112,811; 09/112,812; High efficiency particles may jam 09/112,813; 09/112,814; CMOS the bend actuator 09/112,764; 09/112,765; compatible 09/112,767; 09/112,768 voltages and currents Standard MEMS processes can be used Easy extension from single nozzles to pagewidth print heads High CTE A material with a High force can Requires special U.S. Ser. No. 09/112,778; thermo- very high coefficient be generated material (e.g. 09/112,815; 09/113,096; elastic of thermal Three methods PTFE) 09/113,095; 09/112,808; actuator expansion (CTE) of PTFE Requires a PTFE 09/112,809; 09/112,780; such as polytetra- deposition are deposition 09/113,083; 09/112,793; fluoroethylene under process, which is 09/112,794; 09/113,128; (PTFE) is used. development: not yet standard in 09/113,127; 09/112,756; As high CTE chemical vapor ULSI fabs 09/112,807; 09/112,806; materials are usually deposition PTFE deposition 09/112,820 non-conductive, a (CVD), spin cannot be heater fabricated coating, and followed with from a conductive evaporation high temperature material is PTFE is a (above 350° C.) incorporated. A 50 candidate for processing μm long PTFE bend low dielectric Pigmented inks actuator with constant may be infeasible, polysilicon heater insulation in as pigment and 15 mW power ULSI particles may jam input can provide Very low power the bend actuator 180 μN force and 10 consumption μm deflection. Many ink types Actuator motions can be used include: Simple planar Bend fabrication Push Small chip area Buckle required for Rotate each actuator Fast operation High efficiency CMOS compatible voltages and currents Easy extension from single nozzles to pagewidth print heads Conductive A polymer with a High force can Requires special U.S. Ser. No. 09/113,083 polymer high coefficient of be generated materials thermo- thermal expansion Very low power development elastic (such as PTFE) is consumption (High CTE actuator doped with Many ink types conductive conducting can be used polymer) substances to Simple planar Requires a PTFE increase its fabrication deposition conductivity to Small chip area process, which is about 3 orders of required for not yet standard in magnitude below each actuator ULSI fabs that of copper. The Fast operation PTFE deposition conducting polymer High efficiency cannot be expands when CMOS followed with resistively heated. compatible high temperature Examples of voltages and (above 350° C.) conducting dopants currents processing include: Easy extension Evaporation and Carbon nanotubes from single CVD deposition Metal fibers nozzles to techniques cannot Conductive pagewidth print be used polymers such as heads Pigmented inks doped may be infeasible, polythiophene as pigment Carbon granules particles may jam the bend actuator Shape A shape memory High force is Fatigue limits U.S. Ser. No. 09/113,122 memory alloy such as TiNi available maximum number alloy (also known as (stresses of of cycles Nitinol - Nickel hundreds of Low strain (1%) is Titanium alloy MPa) required to extend developed at the Large strain is fatigue resistance Naval Ordnance available (more Cycle rate limited Laboratory) is than 3%) by heat removal thermally switched High corrosion Requires unusual between its weak resistance materials (TiNi) martensitic state and Simple The latent heat of its high stiffness construction transformation austenic state. The Easy extension must be provided shape of the actuator from single High current in its martensitic nozzles to operation state is deformed pagewidth print Requires pre- relative to the heads stressing to distort austenic shape. The Low voltage the martensitic shape change causes operation state ejection of a drop. Linear Linear magnetic Linear Magnetic Requires unusual U.S. Ser. No. 09/113,061 Magnetic actuators include the actuators can be semiconductor Actuator Linear Induction constructed with materials such as Actuator (LIA), high thrust, long soft magnetic Linear Permanent travel, and high alloys (e.g. Magnet efficiency using CoNiFe) Synchronous planar Some varieties Actuator (LPMSA), semiconductor also require Linear Reluctance fabrication permanent Synchronous techniques magnetic Actuator (LRSA), Long actuator materials such as Linear Switched travel is Neodymium iron Reluctance Actuator available boron (NdFeB) (LSRA), and the Medium force is Requires complex Linear Stepper available multi-phase drive Actuator (LSA). Low voltage circuitry operation High current operation

BASIC OPERATION MODE Description Advantages Disadvantages Examples Actuator This is the simplest Simple Drop repetition Thermal ink jet directly mode of operation: operation rate is usually Piezoelectric ink jet pushes ink the actuator directly No external limited to around U.S. Ser. No. 09/112,751; supplies sufficient fields required 10 kHz. 09/112,787; 09/112,802; kinetic energy to Satellite drops However, this is 09/112,803; 09/113,097; expel the drop. The can be avoided not fundamental 09/113,099; 09/113,084; drop must have a if drop velocity to the method, 09/112,778; 09/113,077; sufficient velocity to is less than 4 but is related to 09/113,061; 09/112,816; overcome the m/s the refill method 09/112,819; 09/113,095; surface tension. Can be efficient, normally used 09/112,809; 09/112,780; depending upon All of the drop 09/113,083; 09/113,121; the actuator kinetic energy 09/113,122; 09/112,793; used must be provided 09/112,794; 09/113,128; by the actuator 09/113,127; 09/112,756; Satellite drops 09/112,755; 09/112,754; usually form if 09/112,811; 09/112,812; drop velocity is 09/112,813; 09/112,814; greater than 4.5 09/112,764; 09/112,765; m/s 09/112,767; 09/112,768; 09/112,807; 09/112,806; 09/112,820 Proximity The drops to be Very simple Requires close Silverbrook, EP 0771 printed are selected print head proximity 658 A2 and related by some manner fabrication can between the print patent applications (e.g. thermally be used head and the induced surface The drop print media or tension reduction of selection means transfer roller pressurized ink). does not need to May require two Selected drops are provide the print heads separated from the energy required printing alternate ink in the nozzle by to separate the rows of the contact with the drop from the image print medium or a nozzle Monolithic color transfer roller. print heads are difficult Electro- The drops to be Very simple Requires very Silverbrook, EP 0771 static pull printed are selected print head high electrostatic 658 A2 and related on ink by some manner fabrication can field patent applications (e.g. thermally be used Electrostatic field Tone-Jet induced surface The drop for small nozzle tension reduction of selection means sizes is above air pressurized ink). does not need to breakdown Selected drops are provide the Electrostatic field separated from the energy required may attract dust ink in the nozzle by to separate the a strong electric drop from the field. nozzle Magnetic The drops to be Very simple Requires Silverbrook, EP 0771 pull on ink printed are selected print head magnetic ink 658 A2 and related by some manner fabrication can Ink colors other patent applications (e.g. thermally be used than black are induced surface The drop difficult tension reduction of selection means Requires very pressurized ink). does not need to high magnetic Selected drops are provide the fields separated from the energy required ink in the nozzle by to separate the a strong magnetic drop from the field acting on the nozzle magnetic ink. Shutter The actuator moves High speed Moving parts are U.S. Ser. No. 09/112,818; a shutter to block (>50 kHz) required 09/112,815; 09/112,808 ink flow to the operation can be Requires ink nozzle. The ink achieved due to pressure pressure is pulsed at reduced refill modulator a multiple of the time Friction and wear drop ejection Drop timing can must be frequency. be very accurate considered The actuator Stiction is energy can be possible very low Shuttered The actuator moves Actuators with Moving parts are U.S. Ser. No. 09/113,066; grill a shutter to block small travel can required 09/112,772; 09/113,096; ink flow through a be used Requires ink 09/113,068 grill to the nozzle. Actuators with pressure The shutter small force can modulator movement need be used Friction and wear only be equal to the High speed must be width of the grill (>50 kHz) considered holes. operation can be Stiction is achieved possible Pulsed A pulsed magnetic Extremely low Requires an U.S. Ser. No. 09/112,779 magnetic field attracts an ‘ink energy external pulsed pull on ink pusher’ at the drop operation is magnetic field pusher ejection frequency. possible Requires special An actuator controls No heat materials for both a catch, which dissipation the actuator and prevents the ink problems the ink pusher pusher from moving Complex when a drop is not construction to be ejected.

AUXILIARY MECHANISM (APPLIED TO ALL NOZZLES) Description Advantages Disadvantages Examples None The actuator directly Simplicity of Drop ejection Most ink jets, including fires the ink drop, construction energy must be piezoelectric and thermal and there is no Simplicity of supplied by bubble. external field or operation individual nozzle U.S. Ser. No. 09/112,751; other mechanism Small physical actuator 09/112,787; 09/112,802; required. size 09/112,803; 09/113,097; 09/113,084; 09/113,078; 09/113,077; 09/113,061; 09/112,816; 09/113,095; 09/112,809; 09/112,780; 09/113,083; 09/113,121; 09/113,122; 09/112,793; 09/112,794; 09/113,128; 09/113,127; 09/112,756; 09/112,755; 09/112,754; 09/112,811; 09/112,812; 09/112,813; 09/112,814; 09/112,764; 09/112,765; 09/112,767; 09/112,768; 09/112,807; 09/112,806; 09/112,820 Oscillating The ink pressure Oscillating ink Requires external Silverbrook, EP 0771 ink oscillates, providing pressure can ink pressure 658 A2 and related pressure much of the drop provide a refill oscillator patent applications (including ejection energy. The pulse, allowing Ink pressure U.S. Ser. No. 09/113,066; acoustic actuator selects higher operating phase and 09/112,818; 09/112,772; stimulation) which drops are to speed amplitude must 09/112,815; 09/113,096; be fired by The actuators be carefully 09/113,068; 09/112,808 selectively blocking may operate controlled or enabling nozzles. with much Acoustic The ink pressure lower energy reflections in the oscillation may be Acoustic lenses ink chamber achieved by can be used to must be designed vibrating the print focus the sound for head, or preferably on the nozzles by an actuator in the ink supply. Media The print head is Low power Precision Silverbrook, EP 0771 proximity placed in close High accuracy assembly 658 A2 and related proximity to the Simple print required patent applications print medium. head Paper fibers may Selected drops construction cause problems protrude from the Cannot print on print head further rough substrates than unselected drops, and contact the print medium. The drop soaks into the medium fast enough to cause drop separation. Transfer Drops are printed to High accuracy Bulky Silverbrook, EP 0771 roller a transfer roller Wide range of Expensive 658 A2 and related instead of straight to print substrates Complex patent applications the print medium. A can be used construction Tektronix hot melt transfer roller can Ink can be dried piezoelectric ink jet also be used for on the transfer Any of U.S. Ser. No. proximity drop roller 09/112,751; 09/112,787; separation. 09/112,802; 09/112,803; 09/113,097; 09/113,099; 09/113,084; 09/113,066; 09/112,778; 09/112,779; 09/113,077; 09/113,061; 09/112,818; 09/112,816; 09/112,772; 09/112,819; 09/112,815; 09/113,096; 09/113,068; 09/113,095; 09/112,808; 09/112,809; 09/112,780; 09/113,083; 09/113,121; 09/113,122; 09/112,793; 09/112,794; 09/113,128; 09/113,127; 09/112,756; 09/112,755; 09/112,754; 09/112,811; 09/112,812; 09/112,813; 09/112,814; 09/112,764; 09/112,765; 09/112,767; 09/112,768; 09/112,807; 09/112,806; 09/112,820; 09/112,821 Electro- An electric field is Low power Field strength Silverbrook, EP 0771 static used to accelerate Simple print required for 658 A2 and related selected drops head separation of patent applications towards the print construction small drops is Tone-Jet medium. near or above air breakdown Direct A magnetic field is Low power Requires Silverbrook, EP 0771 magnetic used to accelerate Simple print magnetic ink 658 A2 and related field selected drops of head Requires strong patent applications magnetic ink construction magnetic field towards the print medium. Cross The print head is Does not Requires external U.S. Ser. No. 09/113,099; magnetic placed in a constant require magnet 09/112,819 field magnetic field. The magnetic Current densities Lorenz force in a materials to be may be high, current carrying integrated in the resulting in wire is used to move print head electromigration the actuator. manufacturing problems process Pulsed A pulsed magnetic Very low power Complex print U.S. Ser. No. 09/112,779 magnetic field is used to operation is head construction field cyclically attract a possible Magnetic paddle, which Small print head materials pushes on the ink. size required in print A small actuator head moves a catch, which selectively prevents the paddle from moving.

ACTUATOR AMPLIFICATION OR MODIFICATION METHOD Description Advantages Disadvantages Examples None No actuator Operational Many actuator Thermal Bubble Ink jet mechanical simplicity mechanisms U.S. Ser. No. 09/112,751; amplification is have 09/112,787; 09/113,099; used. The actuator insufficient 09/113,084; 09/112,819; directly drives the travel, or 09/113,121; 09/113,122 drop ejection insufficient process. force, to efficiently drive the drop ejection process Differential An actuator material Provides greater High stresses Piezoelectric expansion expands more on travel in a are involved U.S. Ser. No. 09/112,802; bend one side than on the reduced print Care must be 09/112,778; 09/112,815; actuator other. The head area taken that the 09/113,096; 09/113,068; expansion may be materials do not 09/113,095; 09/112,808; thermal, delaminate 09/112,809; 09/112,780; piezoelectric, Residual bend 09/113,083; 09/112,793; magnetostrictive, or resulting from 09/113,128; 09/113,127; other mechanism. high 09/112,756; 09/112,755; The bend actuator temperature or 09/112,754; 09/112,811; converts a high high stress 09/112,812; 09/112,813; force low travel during 09/112,814; 09/112,764; actuator mechanism formation 09/112,765; 09/112,767, to high travel, lower 09/112,768; 09/112,807; force mechanism. 09/112,806; 09/112,820 Transient A trilayer bend Very good High stresses U.S. Ser. No. 09/112,767; bend actuator where the temperature are involved 09/112,768 actuator two outside layers stability Care must be are identical. This High speed, as a taken that the cancels bend due to new drop can be materials do not ambient temperature fired before heat delaminate and residual stress. dissipates The actuator only Cancels residual responds to transient stress of heating of one side formation or the other. Reverse The actuator loads a Better coupling Fabrication U.S. Ser. No. 09/113,097; spring spring. When the to the ink complexity 09/113,077 actuator is turned High stress in off, the spring the spring releases. This can reverse the force/distance curve of the actuator to make it compatible with the force/time requirements of the drop ejection. Actuator A series of thin Increased travel Increased Some piezoelectric ink stack actuators are Reduced drive fabrication jets stacked This can be voltage complexity U.S. Ser. No. 09/112,803 appropriate where Increased actuators require possibility of high electric field short circuits strength, such as due to pinholes electrostatic and piezoelectric actuators. Multiple Multiple smaller Increases the Actuator forces U.S. Ser. No. 09/113,061; actuators actuators are used force available may not add 09/112,818; 09/113,096; simultaneously to from an actuator linearly, 09/113,095; 09/112,809; move the ink. Each Multiple reducing 09/112,794; 09/112,807; actuator need actuators can be efficiency 09/112,806 provide only a positioned to portion of the force control ink flow required. accurately Linear A linear spring is Matches low Requires print U.S. Ser. No. 09/112,772 Spring used to transform a travel actuator head area for motion with small with higher the spring travel and high force travel into a longer travel, requirements lower force motion. Non-contact method of motion transformation Coiled A bend actuator is Increases travel Generally U.S. Ser. No. 09/112,815; actuator coiled to provide Reduces chip restricted to 09/112,808; 09/112,811; greater travel in a area planar 09/112,812 reduced chip area. Planar implementations implementations due to extreme are relatively fabrication easy to difficulty in fabricate. other orientations. Flexure A bend actuator has Simple means Care must be U.S. Ser. No. 09/112,779; bend a small region near of increasing taken not to 09/113,068; 09/112,754 actuator the fixture point, travel of a bend exceed the which flexes much actuator elastic limit in more readily than the flexure area the remainder of the Stress actuator. The distribution is actuator flexing is very uneven effectively Difficult to converted from an accurately even coiling to an model with angular bend, finite element resulting in greater analysis travel of the actuator tip. Catch The actuator Very low Complex U.S. Ser. No. 09/112,779 controls a small actuator energy construction catch. The catch Very small Requires either enables or actuator size external force disables movement Unsuitable for of an ink pusher that pigmented inks is controlled in a bulk manner. Gears Gears can be used to Low force, low Moving parts U.S. Ser. No. 09/112,818 increase travel at the travel actuators are required expense of duration. can be used Several actuator Circular gears, rack Can be cycles are and pinion, ratchets, fabricated using required and other gearing standard surface More complex methods can be MEMS drive electronics used. processes Complex construction Friction, friction, and wear are possible Buckle A buckle plate can Very fast Must stay S. Hirata et al, “An Ink-jet plate be used to change a movement within elastic Head Using Diaphragm slow actuator into a achievable limits of the Microactuator”, Proc. fast motion. It can materials for IEEE MEMS, Feb. 1996, also convert a high long device life pp 418-423. force, low travel High stresses U.S. Ser. No. 09/113,096; actuator into a high involved 09/112,793 travel, medium Generally high force motion. power requirement Tapered A tapered magnetic Linearizes the Complex U.S. Ser. No. 09/112,816 magnetic pole can increase magnetic construction pole travel at the expense force/distance of force. curve Lever A lever and fulcrum Matches low High stress U.S. Ser. No. 09/112,755; is used to transform travel actuator around the 09/112,813; 09/112,814 a motion with small with higher fulcrum travel and high force travel into a motion with requirements longer travel and Fulcrum area lower force. The has no linear lever can also movement, and reverse the direction can be used for of travel. a fluid seal Rotary The actuator is High Complex U.S. Ser. No. 09/112,794 impeller connected to a mechanical construction rotary impeller. A advantage Unsuitable for small angular The ratio of pigmented inks deflection of the force to travel actuator results in a of the actuator rotation of the can be matched impeller vanes, to the nozzle which push the ink requirements by against stationary varying the vanes and out of the number of nozzle. impeller vanes Acoustic A refractive or No moving Large area 1993 Hadimioglu et al, lens diffractive (e.g. parts required EUP 550,192 zone plate) acoustic Only relevant 1993 Elrod et al, EUP lens is used to for acoustic ink 572,220 concentrate sound jets waves. Sharp A sharp point is Simple Difficult to Tone-jet conductive used to concentrate construction fabricate using point an electrostatic standard VLSI field. processes for a surface ejecting ink-jet Only relevant for electrostatic ink jets

ACTUATOR MOTION Description Advantages Disadvantages Examples Volume The volume of the Simple High energy is Hewlett-Packard Thermal expansion actuator changes, construction in typically Ink jet pushing the ink in the case of required to Canon Bubblejet all directions. thermal ink jet achieve volume expansion. This leads to thermal stress, cavitation, and kogation in thermal ink jet implementations Linear, The actuator moves Efficient High fabrication U.S. Ser. No. 09/112,751; normal to in a direction normal coupling to ink complexity may 09/112,787; 09/112,803; chip to the print head drops ejected be required to 09/113,084; 09/113,077; surface surface. The nozzle normal to the achieve 09/112,816 is typically in the surface perpendicular line of movement. motion Parallel to The actuator moves Suitable for Fabrication U.S. Ser. No. 09/113,061; chip parallel to the print planar complexity 09/112,818; 09/112,772; surface head surface. Drop fabrication Friction 09/112,754; 09/112,811; ejection may still be Stiction 09/112,812; 09/112,813 normal to the surface. Membrane An actuator with a The effective Fabrication 1982 Howkins push high force but small area of the complexity U.S. Pat. No. 4,459,601 area is used to push actuator Actuator size a stiff membrane becomes the Difficulty of that is in contact membrane area integration in a with the ink. VLSI process Rotary The actuator causes Rotary levers Device U.S. Ser. No. 09/113,097; the rotation of some may be used to complexity 09/113,066; 09/112,818; element, such a grill increase travel May have 09/112,794 or impeller Small chip area friction at a requirements pivot point Bend The actuator bends A very small Requires the 1970 Kyser et al when energized. change in actuator to be U.S. Pat. No. 3,946,398 This may be due to dimensions can made from at 1973 Stemme U.S. Pat. No. differential thermal be converted to least two 3,747,120 expansion, a large motion. distinct layers, 09/112,802; 09/112,778; piezoelectric or to have a 09/112,779; 09/113,068; expansion, thermal 09/112,780; 09/113,083; magnetostriction, or difference 09/113,121; 09/113,128; other form of across the 09/113,127; 09/112,756; relative dimensional actuator 09/112,754; 09/112,811; change. 09/112,812 Swivel The actuator swivels Allows Inefficient U.S. Ser. No. 09/113,099 around a central operation where coupling to the pivot. This motion is the net linear ink motion suitable where there force on the are opposite forces paddle is zero applied to opposite Small chip area sides of the paddle, requirements e.g. Lorenz force. Straighten The actuator is Can be used Requires careful U.S. Ser. No. 09/113,122; normally bent, and with shape balance of 09/112,755 straightens when memory alloys stresses to energized. where the ensure that the austenic phase quiescent bend is planar is accurate Double The actuator bends One actuator Difficult to U.S. Ser. No. 09/112,813; bend in one direction can be used to make the drops 09/112,814; 09/112,764 when one element is power two ejected by both energized, and nozzles. bend directions bends the other way Reduced chip identical. when another size. A small element is Not sensitive to efficiency loss energized. ambient compared to temperature equivalent single bend actuators. Shear Energizing the Can increase the Not readily 1985 Fishbeck actuator causes a effective travel applicable to U.S. Pat. No. 4,584,590 shear motion in the of piezoelectric other actuator actuator material. actuators mechanisms Radial The actuator Relatively easy High force 1970 Zoltan U.S. Pat. No. constriction squeezes an ink to fabricate required 3,683,212 reservoir, forcing single nozzles Inefficient ink from a from glass Difficult to constricted nozzle. tubing as integrate with macroscopic VLSI processes structures Coil/ A coiled actuator Easy to Difficult to U.S. Ser. No. 09/112,815; uncoil uncoils or coils fabricate as a fabricate for 09/112,808; 09/112,811; more tightly. The planar VLSI non-planar 09/112,812 motion of the free process devices end of the actuator Small area Poor out-of- ejects the ink. required, plane stiffness therefore low cost Bow The actuator bows Can increase the Maximum U.S. Ser. No. 09/112,819; (or buckles) in the speed of travel travel is 09/113,096; 09/112,793 middle when Mechanically constrained energized. rigid High force required Push-Pull Two actuators The structure is Not readily U.S. Ser. No. 09/113,096 control a shutter. pinned at both suitable for ink One actuator pulls ends, so has a jets which the shutter, and the high out-of- directly push other pushes it. plane rigidity the ink Curl A set of actuators Good fluid flow Design U.S. Ser. No. 09/113,095; inwards curl inwards to to the region complexity 09/112,807 reduce the volume behind the of ink that they actuator enclose. increases efficiency Curl A set of actuators Relatively Relatively large U.S. Ser. No. 09/112,806 outwards curl outwards, simple chip area pressurizing ink in a construction chamber surrounding the actuators, and expelling ink from a nozzle in the chamber. Iris Multiple vanes High efficiency High fabrication U.S. Ser. No. 09/112,809 enclose a volume of Small chip area complexity ink. These Not suitable for simultaneously pigmented inks rotate, reducing the volume between the vanes. Acoustic The actuator The actuator Large area 1993 Hadimioglu et al, vibration vibrates at a high can be required for EUP 550,192 frequency. physically efficient 1993 Elrod et al, EUP distant from the operation at 572,220 ink useful frequencies Acoustic coupling and crosstalk Complex drive circuitry Poor control of drop volume and position None In various ink jet No moving Various other Silverbrook, EP 0771 658 designs the actuator parts tradeoffs are A2 and related patent does not move. required to applications eliminate Tone-jet moving parts

NOZZLE REFILL METHOD Description Advantages Disadvantages Examples Surface This is the normal Fabrication Low speed Thermal ink jet tension way that ink jets are simplicity Surface tension Piezoelectric ink jet refilled. After the Operational force relatively U.S. Ser. No.-09/112,751; actuator is energized, simplicity small 09/113,084; 09/112,779; it typically returns compared to 09/112,816; 09/112,819; rapidly to its normal actuator force 09/113,095; 09/112,809; position. This rapid Long refill 09/112,780; 09/113,083; return sucks in air time usually 09/113,121; 09/113,122; through the nozzle dominates the 09/112,793; 09/112,794; opening. The ink total repetition 09/113,128; 09/113,127; surface tension at the rate 09/112,756; 09/112,755; nozzle then exerts a 09/112,754; 09/112,811; small force restoring 09/112,812; 09/112,813; the meniscus to a 09/112,814; 09/112,764; minimum area. This 09/112,765; 09/112,767; force refills the 09/112,768; 09/112,807; nozzle. 09/112,806; 09/112,820; 09/112,821 Shuttered Ink to the nozzle High speed Requires U.S. Ser. No. 09/113,066; oscillating chamber is provided Low actuator common ink 09/112,818; 09/112,772; ink at a pressure that energy, as the pressure 09/112,815; 09/113,096; pressure oscillates at twice the actuator need oscillator 09/113,068; 09/112,808 drop ejection only open or May not be frequency. When a close the suitable for drop is to be ejected, shutter, instead pigmented inks the shutter is opened of ejecting the for 3 half cycles: ink drop drop ejection, actuator return, and refill. The shutter is then closed to prevent the nozzle chamber emptying during the next negative pressure cycle. Refill After the main High speed, as Requires two U.S. Ser. No. 09/112,778 actuator actuator has ejected a the nozzle is independent drop a second (refill) actively actuators per actuator is energized. refilled nozzle The refill actuator pushes ink into the nozzle chamber. The refill actuator returns slowly, to prevent its return from emptying the chamber again. Positive The ink is held a High refill rate, Surface spill Silverbrook, EP 0771 658 ink slight positive therefore a must be A2 and related patent pressure pressure. After the high drop prevented applications ink drop is ejected, repetition rate Highly Alternative for: U.S. Ser. No. the nozzle chamber is possible hydrophobic 09/112,751; 09/112,787; fills quickly as print head 09/112,802; 09/112,803; surface tension and surfaces are 09/113,097; 09/113,099; ink pressure both required 09/113,084; 09/112,779; operate to refill the 09/113,077; 09/113,061; nozzle. 09/112,818; 09/112,816; 09/112,819; 09/113,095; 09/112,809; 09/112,780; 09/113,083; 09/113,121; 09/113,122; 09/112,793; 09/112,794; 09/113,128, 09/113,127; 09/112,756; 09/112,755; 09/112,754; 09/112,811; 09/112,812; 09/112,813; 09/112,814; 09/112,764; 09/112,765; 09/112,767; 09/112,768; 09/112,807; 09/112,806; 09/112,820; 09/112,821

METHOD OF RESTRICTING BACK-FLOW THROUGH INLET Description Advantages Disadvantages Examples Long inlet The ink inlet Design Restricts refill Thermal ink jet channel channel to the simplicity rate Piezoelectric ink jet nozzle chamber is Operational May result in a U.S. Ser. No. 09/112,807; made long and simplicity relatively large 09/112,806 relatively narrow, Reduces chip area relying on viscous crosstalk Only partially drag to reduce inlet effective back-flow. Positive The ink is under a Drop selection Requires a Silverbrook, EP 0771 658 ink positive pressure, so and separation method (such A2 and related patent pressure that in the quiescent forces can be as a nozzle rim applications state some of the ink reduced or effective Possible operation of the drop already Fast refill time hydrophobizing, following: protrudes from the or both) to U.S. Ser. No. 09/112,751; nozzle. prevent 09/112,787; 09/112,802; This reduces the flooding of the 09/112,803; 09/113,097; pressure in the ejection 09/113,099; 09/113,084; nozzle chamber surface of the 09/112,778; 09/112,779; which is required to print head. 09/113,077; 09/113,061; eject a certain 09/112,816; 09/112,819; volume of ink. The 09/113,095; 09/112,809; reduction in 09/112,780; 09/113,083; chamber pressure 09/113,121; 09/113,122; results in a 09/112,793; 09/112,794; reduction in ink 09/113,128; 09/113,127; pushed out through 09/112,756; 09/112,755; the inlet. 09/112,754; 09/112,811; 09/112,813; 09/112,814; 09/112,764; 09/112,765; 09/112,767; 09/112,768; Baffle One or more baffles The refill rate is Design HP Thermal Ink Jet are placed in the not as restricted complexity Tektronix piezoelectric ink inlet ink flow. When as the long inlet May increase jet the actuator is method. fabrication energized, the rapid Reduces complexity ink movement crosstalk (e.g. Tektronix creates eddies which hot melt restrict the flow Piezoelectric through the inlet. print heads). The slower refill process is unrestricted, and does not result in eddies. Flexible In this method Significantly Not applicable Canon flap recently disclosed reduces back- to most ink jet restricts by Canon, the flow for edge- configurations inlet expanding actuator shooter thermal Increased (bubble) pushes on ink jet devices fabrication a flexible flap that complexity restricts the inlet. Inelastic deformation of polymer flap results in creep over extended use Inlet filter A filter is located Additional Restricts refill U.S. Ser. No. 09/112,803; between the ink advantage of rate 09/113,061; 09/113,083; inlet and the nozzle ink filtration May result in 09/112,793; 09/113,128; chamber. The filter Ink filter may complex 09/113,127 has a multitude of be fabricated construction small holes or slots, with no restricting ink flow. additional The filter also process steps removes particles which may block the nozzle. Small inlet The ink inlet Design Restricts refill U.S. Ser. No. 09/112,787; compared channel to the simplicity rate 09/112,814; 09/112,820 to nozzle nozzle chamber has May result in a a substantially relatively large smaller cross section chip area than that of the Only partially nozzle, resulting in effective easier ink egress out of the nozzle than out of the inlet. Inlet A secondary Increases speed Requires U.S. Ser. No. 09/112,778 shutter actuator controls the of the ink-jet separate refill position of a shutter, print head actuator and closing off the ink operation drive circuit inlet when the main actuator is energized. The inlet The method avoids Back-flow Requires U.S. Ser. No. 09/112,751; is located the problem of inlet problem is careful design 09/112,802; 09/113,097; behind the back-flow by eliminated to minimize 09/113,099; 09/113,084; ink- arranging the ink- the negative 09/112,779; 09/113,077; pushing pushing surface of pressure 09/112,816; 09/112,819; surface the actuator between behind the 09/112,809; 09/112,780; the inlet and the paddle 09/113,121; 09/112,794; nozzle. 09/112,756; 09/112,755; 09/112,754; 09/112,811; 09/112,812; 09/112,813; 09/112,765; 09/112,767; 09/112,768 Part of the The actuator and a Significant Small increase U.S. Ser. No. 09/113,084; actuator wall of the ink reductions in in fabrication 09/113,095; 09/113,122; moves to chamber are back-flow can complexity 09/112,764 shut off arranged so that the be achieved the inlet motion of the Compact actuator closes off designs possible the inlet. Nozzle In some Ink back-flow None related to Silverbrook, EP 0771 658 actuator configurations of problem is ink back-flow A2 and related patent does not ink jet, there is no eliminated on actuation applications result in expansion or Valve-jet ink back- movement of an Tone-jet flow actuator which may cause ink back-flow through the inlet.

NOZZLE CLEARING METHOD Description Advantages Disadvantages Examples Normal All of the nozzles No added May not be Most ink jet systems nozzle are fired complexity on sufficient to U.S. Ser. No. 09/112,751; firing periodically, before the print head displace dried 09/112,787; 09/112,802; the ink has a chance ink 09/112,803; 09/113,097; to dry. When not in 09/113,099; 09/113,084; use the nozzles are 09/112,778; 09/112,779; sealed (capped) 09/113,077; 09/113,061; against air. 09/112,816; 09/112,819; The nozzle firing is 09/113,095; 09/112,809; usually performed 09/112,780; 09/113,083; during a special 09/113,121; 09/113,122; clearing cycle, after 09/112,793; 09/112,794; first moving the 09/113,128; 09/113,127; print head to a 09/112,756; 09/112,755; cleaning station. 09/112,754; 09/112,811; 09/112,813; 09/112,814; 09/112,764; 09/112,765; 09/112,767; 09/112,768; 09/112,807; 09/112,806; 09/112,820; 09/112,821 Extra In systems which Can be highly Requires Silverbrook, EP 0771 658 power to heat the ink, but do effective if the higher drive A2 and related patent ink heater not boil it under heater is voltage for applications normal situations, adjacent to the clearing nozzle clearing can nozzle May require be achieved by over- larger drive powering the heater transistors and boiling ink at the nozzle. Rapid The actuator is fired Does not Effectiveness May be used with: U.S. Ser. No. succession in rapid succession. require extra depends 09/112,751; 09/112,787; of In some drive circuits on substantially 09/112,802; 09/112,803; actuator configurations, this the print head upon the 09/113,097; 09/113,099; pulses may cause heat Can be readily configuration 09/113,084; 09/112,778; build-up at the controlled and of the ink jet 09/112,779; 09/113,077; nozzle which boils initiated by nozzle 09/112,816; 09/112,819; the ink, clearing the digital logic 09/113,095; 09/112,809; nozzle. In other 09/112,780; 09/113,083; situations, it may 09/113,121; 09/112,793; cause sufficient 09/112,794; 09/113,128; vibrations to 09/113,127; 09/112,756; dislodge clogged 09/112,755; 09/112,754; nozzles. 09/112,811; 09/112,813; 09/112,814; 09/112,764; 09/112,765; 09/112,767; 09/112,768; 09/112,807; 09/112,806; 09/112,820; 09/112,821 Extra Where an actuator is A simple Not suitable May be used with: U.S. Ser. No. power to not normally driven solution where where there is 09/112,802; 09/112,778; ink to the limit of its applicable a hard limit to 09/112,819; 09/113,095; pushing motion, nozzle actuator 09/112,780; 09/113,083; actuator clearing may be movement 09/113,121; 09/112,793; assisted by 09/113,128; 09/113,127; providing an 09/112,756; 09/112,755; enhanced drive 09/112,765; 09/112,767; signal to the 09/112,768; 09/112,807; actuator. 09/112,806; 09/112,820; 09/112,821 Acoustic An ultrasonic wave A high nozzle High U.S. Ser. No. 09/113,066; resonance is applied to the ink clearing implementation 09/112,818; 09/112,772; chamber. This wave capability can cost if 09/112,815; 09/113,096; is of an appropriate be achieved system does 09/113,068; 09/112,808 amplitude and May be not already frequency to cause implemented at include an sufficient force at very low cost in acoustic the nozzle to clear systems which actuator blockages. This is already include easiest to achieve if acoustic the ultrasonic wave actuators is at a resonant frequency of the ink cavity. Nozzle A microfabricated Can clear Accurate Silverbrook, EP 0771 658 clearing plate is pushed severely mechanical A2 and related patent plate against the nozzles. clogged nozzles alignment is applications The plate has a post required for every nozzle. A Moving parts post moves through are required each nozzle, There is risk of displacing dried ink. damage to the nozzles Accurate fabrication is required Ink The pressure of the May be Requires May be used with ink jets pressure ink is temporarily effective where pressure pump covered by U.S. Ser. No. pulse increased so that ink other methods or other 09/112,751; 09/112,787; streams from all of cannot be used pressure 09/112,802; 09/112,803; the nozzles. This actuator 09/113,097; 09/113,099; may be used in Expensive 09/113,084; 09/113,066; conjunction with Wasteful of 09/112,778; 09/112,779; actuator energizing. ink 09/113,077; 09/113,061; 09/112,818; 09/112,816; 09/112,772; 09/112,819; 09/112,815; 09/113,096; 09/113,068; 09/113,095; 09/112,808; 09/112,809; 09/112,780; 09/113,083; 09/113,121; 09/113,122; 09/112,793; 09/112,794; 09/113,128; 09/113,127; 09/112,756; 09/112,755; 09/112,754; 09/112,811; 09/112,812; 09/112,813; 09/112,814; 09/112,764; 09/112,765; 09/112,767; 09/112,768; 09/112,807; 09/112,806; 09/112,820; 09/112,821 Print head A flexible ‘blade’ is Effective for Difficult to use Many ink jet systems wiper wiped across the planar print if print head print head surface. head surfaces surface is non- The blade is usually Low cost planar or very fabricated from a fragile flexible polymer, Requires e.g. rubber or mechanical synthetic elastomer. parts Blade can wear out in high volume print systems Separate A separate heater is Can be effective Fabrication Can be used with many ink ink boiling provided at the where other complexity jets covered by U.S. Ser. No. heater nozzle although the nozzle clearing 09/112,751; 09/112,787; normal drop e- methods cannot 09/112,802; 09/112,803; ection mechanism be used 09/113,097; 09/113,099; does not require it. Can be 09/113,084; 09/113,066; The heaters do not implemented at 09/112,778; 09/112,779; require individual no additional 09/113,077; 09/113,061; drive circuits, as cost in some ink 09/112,818; 09/112,816; many nozzles can be jet 09/112,772; 09/112,819; cleared configurations 09/112,815; 09/113,096; simultaneously, and 09/113,068; 09/113,095; no imaging is 09/112,808; 09/112,809; required. 09/112,780; 09/113,083; 09/113,121; 09/113,122; 09/112,793; 09/112,794; 09/113,128; 09/113,127; 09/112,756; 09/112,755; 09/112,754; 09/112,811; 09/112,812; 09/112,813; 09/112,814; 09/112,764; 09/112,765; 09/112,767; 09/112,768; 09/112,807; 09/112,806; 09/112,820; 09/112,821

NOZZLE PLATE CONSTRUCTION Description Advantages Disadvantages Examples Electro- A nozzle plate is Fabrication High Hewlett Packard Thermal formed separately fabricated simplicity temperatures Ink jet nickel from electroformed and pressures nickel, and bonded are required to to the print head bond nozzle chip. plate Minimum thickness constraints Differential thermal expansion Laser Individual nozzle No masks Each hole must Canon Bubblejet ablated or holes are ablated by required be individually 1988 Sercel et al., SPIE, drilled an intense UV laser Can be quite formed Vol. 998 Excimer Beam polymer in a nozzle plate, fast Special Applications, pp. 76-83 which is typically a Some control equipment 1993 Watanabe et al., polymer such as over nozzle required U.S. Pat. No. 5,208,604 polyimide or profile is Slow where polysulphone possible there are many Equipment thousands of required is nozzles per relatively low print head cost May produce thin burrs at exit holes Silicon A separate nozzle High accuracy Two part K. Bean, IEEE micro- plate is is attainable construction Transactions on Electron machined micromachined High cost Devices, Vol. ED-25, No. from single crystal Requires 10, 1978, pp 1185-1195 silicon, and bonded precision Xerox 1990 Hawkins et al., to the print head alignment U.S. Pat. No. 4,899,181 wafer. Nozzles may be clogged by adhesive Glass Fine glass No expensive Very small 1970 Zoltan U.S. Pat. No. capillaries capillaries are drawn equipment nozzle sizes 3,683,212 from glass tubing. required are difficult to This method has Simple to make form been used for single nozzles Not suited for making individual mass nozzles, but is production difficult to use for bulk manufacturing of print heads with thousands of nozzles. Monolithic, The nozzle plate is High accuracy Requires Silverbrook, EP 0771 658 surface deposited as a layer (<1 μm) sacrificial layer A2 and related patent micro- using standard VLSI Monolithic under the applications machined deposition Low cost nozzle plate to U.S. Ser. No. 09/112,751; using VLSI techniques. Nozzles Existing form the 09/112,787; 09/112,803; litho- are etched in the processes can nozzle 09/113,077; 09/113,061; graphic nozzle plate using be used chamber 09/112,815; 09/113,096; processes VLSI lithography Surface may 09/113,095; 09/112,809; and etching. be fragile to 09/113,083; 09/112,793; the touch 09/112,794; 09/113,128; 09/113,127; 09/112,756; 09/112,755; 09/112,754; 09/112,811; 09/112,813; 09/112,814; 09/112,764; 09/112,765; 09/112,767; 09/112,768; 09/112,807; 09/112,806; 09/112,820 Monolithic, The nozzle plate is a High accuracy Requires long U.S. Ser. No. 09/112,802; etched buried etch stop in (<1 μm) etch times 09/113,097; 09/113,099; through the wafer. Nozzle Monolithic Requires a 09/113,084; 09/113,066; substrate chambers are etched Low cost support wafer 09/112,778; 09/112,779; in the front of the No differential 09/112,818; 09/112,816; wafer, and the wafer expansion 09/112,772; 09/112,819; is thinned from the 09/113,068; 09/112,808; back side. Nozzles 09/112,780; 09/113,121; are then etched in 09/113,122 the etch stop layer. No nozzle Various methods No nozzles to Difficult to Ricoh 1995 Sekiya et al plate have been tried to become clogged control drop U.S. Pat. No. 5,412,413 eliminate the position 1993 Hadimioglu et al EUP nozzles entirely, to accurately 550,192 prevent nozzle Crosstalk 1993 Elrod et al EUP clogging. These problems 572,220 include thermal bubble mechanisms and acoustic lens mechanisms Trough Each drop ejector Reduced Drop firing U.S. Ser. No. 09/112,812 has a trough through manufacturing direction is which a paddle complexity sensitive to moves. There is no Monolithic wicking. nozzle plate. Nozzle slit The elimination of No nozzles to Difficult to 1989 Saito et al instead of nozzle holes and become clogged control drop U.S. Pat. No. 4,799,068 individual replacement by a slit position nozzles encompassing many accurately actuator positions Crosstalk reduces nozzle problems clogging, but increases crosstalk due to ink surface waves

DROP EJECTION DIRECTION Description Advantages Disadvantages Examples Edge Ink flow is along the Simple Nozzles Canon Bubblejet 1979 (‘edge surface of the chip, construction limited to edge Endo et al GB patent shooter’) and ink drops are No silicon High 2,007,162 ejected from the etching required resolution is Xerox heater-in-pit 1990 chip edge. Good heat difficult Hawkins et al U.S. Pat. No. sinking via Fast color 4,899,181 substrate printing Tone-jet Mechanically requires one strong print head per Ease of chip color handing Surface Ink flow is along the No bulk silicon Maximum ink Hewlett-Packard TIJ 1982 (‘roof surface of the chip, etching required flow is Vaught et al U.S. Pat. No. shooter’) and ink drops are Silicon can severely 4,490,728 ejected from the make an restricted U.S. Ser. No. 09/112,787, chip surface, normal effective heat 09/113,077; 09/113,061; to the plane of the sink 09/113,095; 09/112,809 chip. Mechanical strength Through Ink flow is through High ink flow Requires bulk Silverbrook, EP 0771 658 chip, the chip, and ink Suitable for silicon etching A2 and related patent forward drops are ejected pagewidth print applications (‘up from the front heads U.S. Ser. No.09/112,803; shooter’) surface of the chip. High nozzle 09/112,815; 09/113,096; packing density 09/113,083; 09/112,793; therefore low 09/112,794; 09/113,128; manufacturing 09/113,127; 09/112,756; cost 09/112,755; 09/112,754; 09/112,811; 09/112,812; 09/112,813; 09/112,814; 09/112,764; 09/112,765; 09/112,767; 09/112,768; 09/112,807; 09/112,806; 09/112,820; 09/112,821 Through Ink flow is through High ink flow Requires wafer U.S. Ser. No. 09/112,751; chip, the chip, and ink Suitable for thinning 09/112,802; 09/113,097; reverse drops are ejected pagewidth print Requires 09/113,099; 09/113,084; (‘down from the rear heads special 09/113,066; 09/112,778; shooter’) surface of the chip. High nozzle handling 09/112,779; 09/112,818; packing density during 09/112,816; 09/112,772; therefore low manufacture 09/112,819; manufacturing 09/113,068; 09/112,808; cost 09/112,780; 09/113,121; 09/113,122 Through Ink flow is through Suitable for Pagewidth Epson Stylus actuator the actuator, which piezoelectric print heads Tektronix hot melt is not fabricated as print heads require several piezoelectric ink jets part of the same thousand substrate as the connections to drive transistors. drive circuits Cannot be manufactured in standard CMOS fabs Complex assembly required

INK TYPE Description Advantages Disadvantages Examples Aqueous, Water based ink Environmentally Slow drying Most existing ink jets dye which typically friendly Corrosive U.S. Ser. No. 09/112,751; contains: water, dye, No odor Bleeds on 09/112,787; 09/112,802; surfactant, paper 09/112,803; 09/113,097; humectant, and May 09/113,099; 09/113,084; biocide. strikethrough 09/113,066; 09/112,778; Modern ink dyes Cockles paper 09/112,779; 09/113,077; have high water- 09/113,061; 09/112,818; fastness, light 09/112,816; 09/112,772; fastness 09/112,819; 09/112,815; 09/113,096; 09/113,068; 09/113,095; 09/112,808; 09/112,809; 09/112,780; 09/113,083; 09/113,121; 09/113,122; 09/112,793; 09/112,794; 09/113,128; 09/113,127; 09/112,756; 09/112,755; 09/112,754; 09/112,811; 09/112,812; 09/112,813; 09/112,814; 09/112,764; 09/112,765; 09/112,767; 09/112,768; 09/112,807; 09/112,806; 09/112,820; 09/112,821 Silverbrook, EP 0771 658 A2 and related patent applications Aqueous, Water based ink Environmentally Slow drying U.S. Ser. No. 09/112,787; pigment which typically friendly Corrosive 09/112,803; 09/112,808; contains: water, No odor Pigment may 09/113,122; 09/112,793; pigment, surfactant, Reduced bleed clog nozzles 09/113,127 humectant, and Reduced Pigment may Silverbrook, EP 0771 658 biocide. wicking clog actuator A2 and related patent Pigments have an Reduced mechanisms applications advantage in reduced strikethrough Cockles paper Piezoelectric ink-jets bleed, wicking and Thermal ink jets (with strikethrough. significant restrictions) Methyl MEK is a highly Very fast Odorous U.S. Ser. No. 09/112,751; Ethyl volatile solvent used drying Flammable 09/112,787; 09/112,802; Ketone for industrial printing Prints on 09/112,803; 09/113,097; (MEK) on difficult surfaces various 09/113,099; 09/113,084; such as aluminum substrates such 09/113,066; 09/112,778; cans. as metals and 09/112,779; 09/113,077; plastics 09/113,061; 09/112,818; 09/112,816; 09/112,772; 09/112,819; 09/112,815; 09/113,096; 09/113,068; 09/113,095; 09/112,808; 09/112,809; 09/112,780; 09/113,083; 09/113,121; 09/113,122; 09/112,793; 09/112,794; 09/113,128; 09/113,127; 09/112,756; 09/112,755; 09/112,754; 09/112,811; 09/112,812; 09/112,813; 09/112,814; 09/112,764; 09/112,765; 09/112,767; 09/112,768; 09/112,807; 09/112,806; 09/112,820; 09/112,821 Alcohol Alcohol based inks Fast driving Slight odor U.S. Ser. No. 09/112,751; (ethanol, can be used where Operates at Flammable 09/112,787; 09/112,802; 2-butanol, the printer must sub-freezing 09/112,803; 09/113,097; and operate at temperatures 09/113,099; 09/113,084; others) temperatures below Reduced paper 09/113,066; 09/112,778; the freezing point of cockle 09/112,779; 09/113,077; water. An example of Low cost 09/113,061; 09/112,818; this is in-camera 09/112,816; 09/112,772; consumer 09/112,819; 09/112,815; photographic 09/113,096; 09/113,068; printing. 09/113,095; 09/112,808; 09/112,809; 09/112,780; 09/113,083; 09/113,121; 09/113,122; 09/112,793; 09/112,794; 09/113,128; 09/113,127; 09/112,756; 09/112,755; 09/112,754; 09/112,811; 09/112,812; 09/112,813; 09/112,814; 09/112,764; 09/112,765; 09/112,767; 09/112,768; 09/112,807; 09/112,806; 09/112,820; 09/112,821 Phase The ink is solid at No drying High viscosity Tektronix hot melt change room temperature, time - ink Printed ink piezoelectric ink jets (hot melt) and is melted in the instantly typically has a 1989 Nowak U.S. Pat. No. print head before freezes on the ‘waxy’ feel 4,820,346 jetting. Hot melt inks print medium Printed pages U.S. Ser. No. 09/112,751; are usually wax Almost any may ‘block’ 09/112,787; 09/112,802; based, with a melting print medium Ink 09/112,803; 09/113,097; point around 80° C. can be used temperature 09/113,099; 09/113,084; After jetting the ink No paper may be above 09/113,066; 09/112,778; freezes almost cockle occurs the curie point 09/112,779; 09/113,077; instantly upon No wicking of permanent 09/113,061; 09/112,818; contacting the print occurs magnets 09/112,816; 09/112,772; medium or a transfer No bleed Ink heaters 09/112,819; 09/112,815; roller. occurs consume 09/113,096; 09/113,068; No power 09/113,095; 09/112,808; strike through Long warm-up 09/112,809; 09/112,780; occurs time 09/113,083; 09/113,121; 09/113,122; 09/112,793; 09/112,794; 09/113,128; 09/113,127; 09/112,756; 09/112,755; 09/112,754; 09/112,811; 09/112,812; 09/112,813; 09/112,814; 09/112,764; 09/112,765; 09/112,767; 09/112,768; 09/112,807; 09/112,806; 09/112,820; 09/112,821 Oil Oil based inks are High solubility High viscosity: U.S. Ser. No. 09/112,751; extensively used in medium for this is a 09/112,787; 09/112,802; offset printing. They some dyes significant 09/112,803; 09/113,097; have advantages in Does not limitation for 09/113,099; 09/113,084; improved cockle paper use in ink jets, 09/113,066; 09/112,778; characteristics on Does not wick which usually 09/112,779; 09/113,077; paper (especially no through paper require a low 09/113,061; 09/112,818; wicking or cockle). viscosity. 09/112,816; 09/112,772; Oil soluble dies and Some short 09/112,819; 09/112,815; pigments are chain and 09/113,096; 09/113,068; required. multi-branched 09/113,095; 09/112,808; oils have a 09/112,809; 09/112,780; sufficiently 09/113,083; 09/113,121; low viscosity. 09/113,122; 09/112,793; Slow drying 09/112,794; 09/113,128; 09/113,127; 09/112,756; 09/112,755; 09/112,754; 09/112,811; 09/112,812; 09/112,813; 09/112,814; 09/112,764; 09/112,765; 09/112,767; 09/112,768; 09/112,807; 09/112,806; 09/112,820; 09/112,821 Micro- A microemulsion is a Stops ink bleed Viscosity U.S. Ser. No. 09/112,751; emulsion stable, self forming High dye higher than 09/112,787; 09/112,802; emulsion of oil, solubility water 09/112,803; 09/113,097; water, and surfactant. Water, oil, and Cost is slightly 09/113,099; 09/113,084; The characteristic amphiphilic higher than 09/113,066; 09/112,778; drop size is less than soluble dies water based 09/112,779; 09/113,077; 100 nm, and is can be used ink 09/113,061; 09/112,818; determined by the Can stabilize High surfactant 09/112,816; 09/112,772; preferred curvature of pigment concentration 09/112,819; 09/112,815; the surfactant. suspensions required 09/113,096; 09/113,068; (around 5%) 09/113,095; 09/112,808; 09/112,809; 09/112,780; 09/113,083; 09/113,121; 09/113,122; 09/112,793; 09/112,794; 09/113,128; 09/113,127; 09/112,756; 09/112,755; 09/112,754; 09/112,811; 09/112,812; 09/112,813; 09/112,814; 09/112,764; 09/112,765; 09/112,767; 09/112,768; 09/112,807; 09/112,806; 09/112,820; 09/112,821 

We claim:
 1. A method of generating print data from a printed image produced by a printing device operating at a first dots per inch (dpi) value, so that the image is composed of a plurality of dots, the image incorporating defects resulting during printing of the image, such as rotation of a print medium and blemishes of the image, the method comprising the steps of: scanning the printed image, at a sampling rate which corresponds to a second dpi value that exceeds the first dpi value by a predetermined factor, which is such that each dot of the image results in the generation of a set of at least two markers; generating data relating to the position and color value of each marker; detecting the defects in the image and assigning a data value to such defects; processing said data and applying the data value assigned to the defects to determine which of each of the markers generated for a respective dot should be recorded as a center for that dot; and generating print data as a result of the processing step, the print data relating to the position and print value of the markers determined as a result of processing the data.
 2. A method as claimed in claim 1, which includes scanning the image at a sampling rate which corresponds to the second dpi value that exceeds the first dpi value by a factor of three, so that each dot of the image results in the generation of a set of three markers.
 3. A method as claimed in claim 1, which includes carrying out the scanning step at a point upstream of a printing step earred out by the apparatus.
 4. A method as claimed in claim 1, which includes the step of detecting the defects by determining the degree of rotation of the printed image, during the printing step.
 5. A method as claimed in claim 1, in which the step of processing the data and applying the data value assigned to the defects includes the steps of: (a) selecting data relating to an initial group of sets of markers and applying the defect value to the selected data to determine which marker of each selected set is to be recorded as related to the center associated with that set; (b) determining which marker of each set of at least one further set should be recorded as a center of a corresponding dot by using a relationship existing between the positions of the recorded markers of the initial group of sets; (c) adding data related to the position of the, or each, marker, recorded as a result of the determination, to the data relating to recorded markers of the initial group of sets of markers; and (d) repeating steps (b) and (c) until print data for a further, substantially identical image is obtained.
 6. A method as claimed in claim 1, which includes the step of printing an image with said apparatus, using said generated print data.
 7. An apparatus for generating print data from a printed image, the apparatus comprising: a printing device that operates at a first dots per inch (dpi) value to generate the printed image, so that the image is composed of a plurality of dots, the image incorporating defects resulting during printing of the image, such as rotation of a print medium and blemishes of the image; a scanning device positioned downstream of the printing device for scanning the printed image, the scanning device being configured to operate at a sampling rate which corresponds to a second dpi value that exceeds the first dpi value by a predetermined factor, which is such that each dot of the image results in the generation of a set of at least two markers, the scanning device being configured to generate data relating to the position and color value of each marker; and a processor that is connected to the scanning device and is configured to receive said data from the scanning device, the processor being capable of analysing said data for the defects, applying a data value to the defects, and processing said data together with the data value to determine which of each of the markers generated for a respective dot should be recorded as a center for that dot, and generating print data relating to the position and color value of the markers so determined.
 8. An apparatus as claimed in claim 7, in which the printing device is in the form of an inkjet printer.
 9. An apparatus as claimed in claim 7, in which the scanning device is configured to operate at a sampling rate which corresponds to the second dpi value that exceeds the first dpi value by a factor of three, so that each dot of the image results in the generation of a set of three markers.
 10. An apparatus as claimed in claim 7, in which the scanning device includes a series of staggered charge-coupled device (CCD) arrays to achieve the sampling rate corresponding to the second dpi value.
 11. An apparatus as claimed in claim 7, in which the processor is operatively connected with the printing device so that the processor can generate said defect value while the image is printed.
 12. An apparatus as claimed in claim 11, in which the processor is operatively connected with the printing device so that the processor can assign said defect value to a degree of rotation of the image while the image is printed.
 13. An apparatus as claimed in claim 12, in which the processor is pre-programmed to carry out the following steps: (a) selecting data relating to an initial group of sets of markers and applying the defect value to the selected data to determine which marker of each selected set is to be recorded as related to the center associated with that set; (b) determining which marker of each set of at least one further set should be recorded as a center of a corresponding dot by using a relationship existing between the positions of the recorded markers of the initial group of sets; (c) adding data related to the position of the, or each, marker, recorded as result of the determination, to the data relating to recorded markers of the initial group of sets of markers; and (d) repeating steps (b) and (c) until print data for a further, substantially identical image is obtained.
 14. An apparatus as claimed in claim 13, which includes a memory arrangement that is connected to the processor to store the print data.
 15. An apparatus as claimed in claim 13, in which the processor and the memory arrangement are operatively connected to the printing device so that the printing device can print, on demand, said further, substantially identical image.
 16. A digital camera which includes an apparatus as claimed in claim
 7. 17. A digital camera as claimed in claim 16, in which the processor is defined by a processor unit of a digital camera and the memory arrangement is defined by a memory device of the digital camera. 